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From: edhall@randvax.UUCP (Ed Hall)
Newsgroups: comp.sys.ibm.pc
Subject: Need info on 16-bit DMA for AT
Keywords: 8237-5, AT Bus
Message-ID: <1901@randvax.UUCP>
Date: 8 Mar 89 17:44:31 GMT
Organization: Rand Corp., Santa Monica, Ca.
Lines: 18

I'm developing (for my own education) an AT interface card using
DMA for data transfers.  I know how to do this for PC's, and by
extention, how to do 8-bit DMA interfaces for the AT.  But what
is different about the 16-bit channels on the AT?

For instance, I know that the second DMA controller (channels 5 through
7) control address lines A1-A16, thus covering a 128K window of two-byte
words.  Other than this, what is different about 16-bit DMA?  Is the MEM
CS16 signal asserted by the AT during DMA reads?  Writes?  How about I/O
CS16?  What is the layout of the channel 5-7 page registers?

I've got piles of documentation but nothing answers these particular
questions.  Help me graduate from 8 to 16 bits!  Answers or pointers
to documentation are both appreciated.

		-Ed Hall
		edhall@rand.org
		uunet!sdcrdcf!randvax!edhall